Betty Jo Trimble, always known as Bjo, is an LA-area fan. She is married to John Trimble

Betty Jo McCarthy came into fandom through TASFiC, the 1952 Worldcon. She was a WAVE stationed at Naval Station Great Lakes who happened to see an announcement in Astounding about the upcoming convention. She attended and met other fans including Robert Bloch, Willy Ley, and August Derleth; and claims that Harlan Ellison, "this bespectacled young man who had just sold his first short story", "decided he liked me and proposed on the spot." (She declined.)

Bjo was honorably discharged (for bad feet and ankles) in 1953, and soon after married Don Wells. (Her first issue of Pas-Tell was under the name "Bjo Wells".) She says that Don's "jealousy built up until it reached a stage where he'd pop into the house with a loaded .38 to 'catch me' with someone else." (APA-L #105) Bjo and Don were divorced after three years of marriage.

She was an artist and cartoonist, so she was recruited to contribute illos for fanzines. She joined LASFS and met John Trimble under Forrest J Ackerman’s piano, where several fans had taken refuge during a particularly crowded party. "John was in the Air Force, so he and I traded Stupid Officer Stories and discovered we liked each other a lot."

The Trimbles' most famous cause was the successful Save Star Trek campaign, generally credited with allowing the series to run for a third season rather than being canceled after two. They also ran the campaign to have the first of NASA's space shuttles named Enterprise. Her efforts earned her an uncredited role as a crew member in Star Trek: The Motion Picture, along with a contingent of other members of fandom who were allowed to serve as extras in full costume. Fanzines included Where No Fan Has Gone Before.

A later cause, which was less successful, was promoting the Hubbard book Battlefield Earth for which Bjo and John founded a Hollywood-style fanclub (supported by an anonymous donor in 1983. It attempted to get a Hugo for Hubbard, but failed to get his book on the ballot. See File 770 #40 p4 for details.